Conventionally, a passivation layer is formed over a semiconductor device to protect the semiconductor device from deterioration, physical damage and the like. Usually, such a passivation layer is made of silicon nitride and is formed by a plasma CVD process. A silicon nitride is a permeability-resist material, through which an ultraviolet light hardly passes. Therefore, a passivation layer of a silicon nitride is difficult to use for a semiconductor device including a photodiode, which operates in response to a light supplied from an external device.
On the other hand, if a passivation layer having a high permeability is formed over the semiconductor device, a light may be entered into the semiconductor device from undesired angles. For example, an ultraviolet light may be entered from a direction that is inclined from a vertical direction to a sensing area of the photodiode. As a result, the sensitivity of the photodiode may be decreased.
For reference, a semiconductor device in the same technical field as the present invention is disclosed in Japan Patent Publication No. 2002-246576A. The semiconductor device includes a photodiode (12), conductive wiring layers, interlayer insulating layers, and a passivation layer (17). A feature of this invention is that the upper-most conductive wiring is re-arranged to make a wide-opened area above the photodiode. According to such a feature, the sensitivity of a photodiode could be improved. However, an inclined light may still be entered into the photodiode.